Automatic voltage regulator



April 17, 1934. R, A. BRADEN AUTOMATIC VOLTAGE REGULATOR Filed April 7,1930 INVENTOR RENE A BR DEN BY 7%@ ATTORNEY Patented Apr. 17, 1934PATENT OFFICE AUTOMATIC VOLTAGE REGULATOR Rene A. Braden, Merchantville,N. Radio Corporation of America.

Delaware J., assigner to a. corporation of Application April 7, 1930,Serial No. 442,239

4 Claims.

My present invention relates to voltage regulators, and moreparticularly to an automatic voltage regulator for electron dischargedevices.

In operating a socket-power radio receiver, it may practically proveexpensive to accept the usual 110 volt lighting current at its facevalue. In many sections the usual lighting current measures anywherefrom 90 to 130 volts. In some sections the voltage may drop as low as80, while in other sections the voltage may rise as high as 140. Thenatural consequence of such fluctuation, particularly where thefluctuation rises above rated voltage, is prematurely burned out radiotubes.

The disadvantages that arise at excessive line voltage and insuicientline voltage, are similar in their disturbing influence. With excessiveline voltage the set may operate with greater power, but the electrondischarge tubes may be under 'constant strain. The radio tubes may burnout in short order, resulting in costly operation.r In case there isinsufficient line voltage, the radio set operates usually with weakvolume and poor tonal quality. Accordingly, it can be seen that if linevoltages were constantly high or low,

the problem could be solved by various expediencies. Instead, however,line voltages usually fluctuate from high to low throughout the day andat indefinite intervals. For example, within a few minutes there may bean enormous difference in line voltage, with consequent disastrouseffects on tubes.

Now, I have discovered, and devised means for utilizing a method formaintaining a feeding voltage to the tubes within a slight percentage ofradio tube guaranties. According to my present invention a circuit isarranged, and associated with the power transformer of the lightingcurrent supply, for maintaining constant filament current in theelectron discharge devices, particularly of a radio receiver, in spiteof varying line voltage. Briefly, the present method utilizes anauxiliary circuit coupled to the power transformer, which auxiliarycircuit is employed for producing in the circuits of the filaments to beprotected, a regulating voltage which constantly opposes andsubstantially balances out, the increment of voltage created by theabnormal line voltage increase or decrease.

Accordingly, it is one of the main objects of my present invention toprovide a method of, and employ means for, maintaining constant filamentcurrent flow in electron discharge devices, particularly employed inradio receivers, with varying line voltage, the method consisting inproviding an additional circuit, in the power transformer circuit, forproducing a voltage constantly preventing disturbances caused byvoltages greater or less than a predetermined, desired line voltage.

Another important object of the present invention is to provide in aradio receiver employing one or more electron discharge devices, whichradio receiver is operated by socket-power from the usual 110 voltlighting current source, a circuit associated with the powertransformer, and including an element, the resistance of which fallsproportionally with increased applied voltage, and which circuit iscoupled to the filament circuit of the electron discharge device in sucha manner that voltages above or below 110 volts in the filament circuitare prevented by a regulating voltage produced by the said auxiliarycircuit.

Other objects of the invention are to improve generally the simplicityand efficiency of automatic voltage regulators for radio receivers, andto provide an automatic line voltage regulator which is not only durableand reliable in operation, but economically arranged in a radioreceiver.

The novel features which I believe to be characteristic of my inventionare set forth in particularity in the appended claims, the inventionitself, however, as to both its organization and method of operationwill best be understood by reference to the following description takenin connection with the drawing in which I have indicateddiagrammatically several circuit organizations whereby my invention maybe carried into effect.

In the drawing,

Fig. 1 diagrammatically shows a circuit embodying the invention,

Fig. 2 graphically shows the operation of the invention,

Fig. 3 represents graphically the ideal and the actual carbon filamentlamp characteristics,

Fig. 4 diagrammatically shows a modified form of the invention,

Fig. 5 graphically presents the characteristics of the modificationshown in Fig. 4.

Referring to the accompanying drawing there is shown an electrondischarge device 1 including the usual control electrode, cathode andanode. It is of course understood that the electron discharge device canbe a tetrode or even a pentode tube. It is further pointed out that thedevice canbe of the type wherein an indirectly heated cathode isemployed, it being only essential to the sok -9 also being in serieswith the winding 6.

present invention that the iilament 2 be energized and heated from asource of current 3, the latter in this case being the usual 110 voltalternating current source utilized for lighting current.

As is well known to those skilled in the art the source 3 is connectedto the filament of each tube through a power transformer 4, the primary5 of which is directly connected to the source 3, and the secondary 6,of which device, is connected to the filament circuit of the tube ortubes. In the drawing I have only shown one electron discharge device,the circuit between the grid and filament of the device being termedinput, While the circuit between the anode and filament is termedoutput.

It is to be understood that the device l is symbolic of all the tubesgenerally employed in a `i'adio receiver, and that the circuit betweenthe filament of the device 1 of the secondary 6 of the transformer mayhave in it the filaments of other tubes used in the radio receiver. Ihave further designated at 7', the potentiometer shunted across theiilament 2 in order to adjust the Voltage on the iilament to obtain auniform potential drop across the filament. This device is well known inalternating current operated radio receivers, and need not be describedin any further details.

An auxiliary circuit, generally designated as A, is provided in thepower circuit of the receiver. This auxiliary circuit includes a coil 6which acts as an independent secondary winding of the power transformer4. A transformer I is provided between the filament circuit and the aux--iliary circuit A for coupling the two circuits for a reason to bepresently explained. The primary winding 8 of the transformer 7 hasconnected with it in series the carbon iilament 9 of an incandescentcarbon filament lamp 10, the filament The secondary 11 of thetransformer 7 is connected in series with the filament 2, and thesecondary 6 in the electron discharge lament circuit.

It will be readily seen that the voltage in the primary 5 of the powertransformer 4 induces a current I1 in the electron dischargeiilamentcircuit, it being assumed to iiow in the direction of the arrow;and, also, a current I2 in the carbon filament circuit, flowing in thedirection of the arrow. As the line voltage increases, the current I1 inthe electron discharge filament circuit tends to increase. I-Iowever,due to the fact that the resistance cf the carbon lament 9 decreases asthe current I2 increases, it will be seen that the current I2 in theauxiliary circuit A increases more rapidly than current I1.

The windings 8, 1l of transformer '7 are so arranged between theauxiliary circuit A and the electron discharge lament circuit that the`voltage E, induced in the electron discharge iilament circuit by thetransformer 7, opposes the main voltage in the electron dischargeiilament circuit, and consequently prevents most of the change incurrent I1, the direction of the voltage -E in the electron dischargelament circuit beby plotting the resistance of the filament 9 in ohmsagainst current in amperes.

There is thus obtained a curve representing the relation between Ii, I2with change of resistance of the filament 9 of the carbon lamp 10 incircuit A.

`These curves are obtained, from actual calculan tions and theoreticalconsiderations of the characteristics of the voltage regulator, from thefollowing table:

, Drop R E I i I 2 across R/ Ohms Volts Ampercs Amperes Volts 100 11. 41 10 10 50 1l. 65 1 20 10 2U l2. 5 1 50 10 l0 14. 14 1 l. 0 10 5 18. 0 12. 0 10 2 3l. 5 1 5.0 10 l 55.8 1 10.0 10

The symbol R designates the resistance of the filament 9 of the carbonlamp 10; the symbol E represents the voltage from source 3; the symbolsI1 and I2 represent the currents flowing respectively in the electrondischarge tube iilament circuit and the regulating circuit A; while, thelast column indicates values for the voltage drop across the carbon lampfilament 9. The various values in the last two tables were obtained bykeeping Ii constant, E and R varying as indicated in the table. It Willbe noted that the last two columns of the table show whatcharacteristics are required for the carbon lament lamp l0 in circuit A.

It will be noted that the voltage drop across R is constant. This is theideal condition, but it cannot be attained in practice. The closer thecarbon filament comes to having this characteristie, the more constantthe iilament current will be with varying line voltage. Thesecalculations are based on the assumption that the resistance R of lament2 is constant. If the element R had ideal characteristics, it would notmatter whether or not the tube filament resistance R was affected by thecurrent iiowing through it, for the current would be constant. But in anactual circuit, the lament resistance R will increase as the iilamentcurrent increases. This dependence of iilament i'esistance on currentwill cooperate with the change of R in holding I1 nearly constant.

The ideal and the actual carbon lament lamp characteristics Vareplotted, and graphically shown, in Fig. 3. This graph shows filamentcurrent in carbon lamp as abscissee and Volts across carbon filament asordinates, three curves being shown in the graph. The curve in full lineis designated as the actual curve; the ideal curve is shown in dottedlines; while the constant resistance line curve is shown in dotted line.Three Values, a, b, c of filament current in the carbon lamp are shownas dotted spaced vertical lines, the value c being designated as themaximum safe current.

Currents below the value a do not heat the iilament peiceptibly, andconsequently the resistance is constant. If the current is increasedbeyond this point, the filament is likely to burn out. If the circuit isadjusted so that, at normal line voltage, the current in the carbon lampis a,

there will be no effect if the line voltage drops voltage falls to sucha value that the carbon lilarnent current drops below the value a, thecompensation ceases, and variations of line voltage producecorresponding changes in the vacuum tube filament current. If the linevoltage increases suiciently to raise the carbon filament current to c,this lament is likely to burn out, as mentioned above. However, thenormal operating point may be put far enough below the danger point toeliminate the possibility of such trouble.

In Fig. i there is shown a modified form of the invention, in which agas-filled discharge tube, such as a neon tube, can be used in place ofthe carbon ilament lamp. Thus a neon tube 10, conventionallyrepresented, is shown connected in the circuit A in Fig. 4. The circuitis otherwise the same, and therefore is not shown with all the detailsof Fig. 1, it being understood that the remaining details of the circuitare the same as in l. The neon tube can be of any well knownconstruction, such as the nat-plate neon tube commonly used intelevision receivers.

The characteristics of a neon lamp are graphically shown in Fig. 5wherein current through neon lamp as abscissae are plotted against voltsacross lamp as ordinates. The curve shown in full line in Fig. 5 is theactual curve` while the curve shown in dotted line is the idealcharacteristic curve. The striking Voltage of the lamp is represented onthe drawing by the arrowheaded vertical line. It will be noted that theactuai characteristic curve is very close `to the ideal curve, and goodvoltage regulation can be obtained with this type of lamp. To produceregulation, the voltage applied to the neon lamp must be above thestriking voltage (i. e. starting voltage) Since the neon lamp may havehigher resistance, and carry less current, than a carbon filament lamp,a different transformer to couple the compensating circuit to the vacuumtube circuit may be required. Whichever type of lamp is used, the turnsratio of this transformer are to be adapted to the currents and voltagesin the two circuits. Thus, if the vacuum tube filaments carry a largecurrent, and the neon lamp (or carbon niament lamp) carries a smallcurrent, the coupling transformer will have a winding of a small numberof turns in series with the vacuum tube filaments, and a winding with alarger number of turns in the neon or carbon lamp circuit.

It will therefore be seen that even though the line voltage luotuatesfrom high to low throughout the day and at indefinite intervals, inspite of the fact that in a few minutes there may arise an enormousdiierence in line voltage, the auxiliary circuit A neverthelessconstantly produces in the electron discharge filament circuit anauxiliary voltage which constantly prevents disturbances produced byvoltages in the electron discharge filament circuit above or below apredetermined normal operating line voltage.

It is to be understood that the present method and arrangement is notlimited to use with an alternating current supply, but may be employedfor any iuctuating current source, the essential feature of theinvention residing in the provision of an auxiliary circuit forutilizing an increase or decrease in voltage to produce an additionalvoltage to prevent disturbance due to the increase or decrease ofvoltage above or below normal operating voltage.

Again, while I have indicated and described two arrangements forcarrying my invention into effect, it will be apparent to one skilled inthe art that my invention is by no means limited to the particularorganizations shown and described, but that many modications may be madewithout departing from the scope of my invention as set forth in theappended claims.

What I claim is:

1. In combination with a thermionic discharge device provided with anelectron emission element, a source of energizing current, a circuitbetween said source and said element whereby potential from said sourcemay be applied to said element, an auxiliary circuit connected to saidsource and including a member whose conductance is directly proportionalto flow of current through the circuit, said auxiliary circuit beingcoupled to said rst circuit in such a manner that changes in potentialof said source above or below a predetermined operating potential aresubstantially balanced out by potential induced in said rst circuit fromsaid auxiliary circuit.

2. In combination with a thermionic discharge device provided with afilament, a source of filament heating current, a circuit between saidsource and said element and including a transformer, an auxiliarycircuit coupled to said transformer and including a. device whoseconductance is directly proportional to iloiv of current therethrough,and a transformer coupling said first circuit and auxiliary circuit insuch a manner that changes in potential oi said source above or below apredetermined operating potential are substantially eliminated.

3. In combination with a thermionic discharge device provided with afilament, a source of lament heating current, a circuit between saidsource and said element and including a transformer, an auxiliarycircuit coupled to said transformer and including a gaseous dischargetube whose conductance is directly proportional to flow of currenttherethrough, and a transformer coupling said first circuit andauxiliary circuit in such a manner that changes in potential of saidsource above or below a predetermined operating potential aresubstantially eliminated.

4. In combination with a thermionic discharge device provided with alament, a source of filament heating current, a circuit between saidsource and said element and including a transformer, an auxiliarycircuit coupled to said transformer and including a neon discharge tubewhose conductance is directly proportional to flow of currenttherethrough, and a transformer coupling said first circuit andauxiliary circuit in such a, manner that changes in potential of saidsource above or below a predetermined operating potential aresubstantially eliminated.

RENE A. BRADEN.

